Removal Of Phenanthrene From Aqueous Solution Through Gemini-modified Sepiolite

With the rapid development of industry, the demand for crude and refined oil products also increases. A number of Polycyclic Aromatic Hydrocarbons (PAHs) are generated during the processes of exploitation, refining, fuel combustion and transportation. PAHs are hydrophobic organic compounds which are ubiquitous in environment and difficult to be removed using traditional remediation method. Therefore, it is extremely urgent to find a economic and effective technology to treat the wastewater containning PAHs. Sepiolite is a natural nonmetal mineral of good physicochemical properties and low price. It has been widely used in the field of various wastewater treatment as an adsorbent. The modified sepiolite which retained its original crystal structure shows a better adsorbability to the organic compounds. But less data has been reported on the sorption of PAHs on sepiolite.The sorption of phenanthrene onto natural and gemini-modified sepiolite was investigated in a batch system. The characterizations of gemini-modified sepiolite were examined by the FT-IR technique. The effects of contact time, pH, ionic strength and temperature on the sorption process were examined. The Freundlich sorption model was applied to describe the equilibrium isotherms and the isotherm constants were determined. The Freundlich model fitted experimental data well. The evaluation of the thermodynamic parameters indicated that the sorption of phenanthrene onto gemini-modified sepiolite was a spontaneous and exothermic process. Compared to the pseudo-second-order kinetic model, the experimental data fitted better with the pseudo-first-order kinetic model. This study can provide a reference on potential use of gemini-modified sepiolite in the water remediation process of PAHs.Meanwhile, Batch sorption experiments were carried out in order to evaluate the maximum sorption conditions of the phenanthrene from aqueous solutions on gemini-modified sepiolite using a 34 full factorial design. The four factors were the initial concentration of phenanthrene, temperature, the initial pH of the solution, and the ionic strength of the dispersion. The optimization of the factors to obtain maximum adsorption was carried out by incorporating effect plots, normal probability plots, interaction plots, analysis of variance (ANOVA). The results indicated that the main effect of ionic strength was the most significant. The interaction of ionic strength and temperature was the most significant. From low level to middle level, the main effect and interaction of each factor was different with the effect from middle level to high level. It showed that the sorption process was nonlinear. Research on middle level of factor was necessary.